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I've been having a similar issue, my gauge will read slightly below dead center, then rise slightly to about a needles width above dead center, then shoot down to just above the cold line. Normally it would be dead center, or maybe slightly below dead center.

a vid of my car:

Now it mainly just runs colder than usual, then slightly warmer when I get on it, only to quickly cool down again. Mostly only happens on really cold days

So I have read mostly all the posts and I still dont get what I should be looking for or looking out for, so I will just explain what I have seen my gauge do.
* (based on tempture read on the in-car tempature guage)
03' 325i
Average day temps with normal everyday driving......dead center 12'oclock
Cold mornings (*30-35 degrees* ) with a 15-20min drive to work the needle will reach half way to dead center
extremly cold mornings/days (*30 and lower) same 15-20 min drive needle wont really even go past the blue square much less the first white line

this will even happen if I go to a freinds house and the car sits for a few hours after runing and its a 34-36 degree high day. It doesnt really bug me- to me its just that its cold out and with a fan that runs when the car is on, its gonna take alot of drving or constant stop and go traffic to get the needle at dead center.

Just thought I would throw out what mine does and see if I should start saving my pennys or start looking at parts.

So I have read mostly all the posts and I still dont get what I should be looking for or looking out for, so I will just explain what I have seen my gauge do.
* (based on tempture read on the in-car tempature guage)
03' 325i
Average day temps with normal everyday driving......dead center 12'oclock
Cold mornings (*30-35 degrees* ) with a 15-20min drive to work the needle will reach half way to dead center
extremly cold mornings/days (*30 and lower) same 15-20 min drive needle wont really even go past the blue square much less the first white line

this will even happen if I go to a freinds house and the car sits for a few hours after runing and its a 34-36 degree high day. It doesnt really bug me- to me its just that its cold out and with a fan that runs when the car is on, its gonna take alot of drving or constant stop and go traffic to get the needle at dead center.

Just thought I would throw out what mine does and see if I should start saving my pennys or start looking at parts.

now I think your thermostat is going bad or your coolent has air in it.
we are talking about 1mm off dead center position.

This is an extremely useful post! I thought I was the only one that had this issue. Honestly, the gauge reading is somewhat sporadic. Sometimes it's dead center and sometimes it's 1mm to the right. I have checked the temp reading on the gauge and everything is indeed fine!

I will start off with the easiest soloution and check for air in the coolant. thanks for and easy answer.

You won't learn anything by doing that. You will only put yourself on a path to purchasing a high-powered rifle and climbing a clock tower screaming, "I can't figure out what the hell is wrong with it!"

Do you know the term, splitting hairs. You are putting far too fine a point on the information displayed by the temp gauge.

So I have read mostly all the posts and I still dont get what I should be looking for or looking out for, so I will just explain what I have seen my gauge do.
* (based on tempture read on the in-car tempature guage)
03' 325i
Average day temps with normal everyday driving......dead center 12'oclock
Cold mornings (*30-35 degrees* ) with a 15-20min drive to work the needle will reach half way to dead center
extremly cold mornings/days (*30 and lower) same 15-20 min drive needle wont really even go past the blue square much less the first white line

this will even happen if I go to a freinds house and the car sits for a few hours after runing and its a 34-36 degree high day. It doesnt really bug me- to me its just that its cold out and with a fan that runs when the car is on, its gonna take alot of drving or constant stop and go traffic to get the needle at dead center.

Just thought I would throw out what mine does and see if I should start saving my pennys or start looking at parts.

maybe the correct ratio of coolant - water was not used, or maybe non oem fluid was used. Has the fluid been replaced recently?

yeah. It hasnt moved even this 1mm towards hot that everyone is talking about since I bought it and I have gone on multiple 2-3 hour(one way) trips (atleast 4 times) since then so like I said its not buging but now I know something could/is not acting right so Im going to keep a closer eye on it. until it starts getting warmer out and I can get some work done on it atleast.

yeah. It hasnt moved even this 1mm towards hot that everyone is talking about since I bought it and I have gone on multiple 2-3 hour(one way) trips (atleast 4 times) since then so like I said its not buging but now I know something could/is not acting right so Im going to keep a closer eye on it. until it starts getting warmer out and I can get some work done on it atleast.

I swear to God, it you ever complain of the needle moving 1mm again, I'm coming over to your house to slap you. You are complaining about a perfectly normal condition.

If _anything_, you have experienced the first pangs of pain from a thermostat that sticks closed, although that is very rare in a BMW. A t-stat that is stuck closed is a huge problem, and the most common failure mode for BMW is that they stick open. I'm not sure how this happens, but cold engines are far and away more common reports of t-stat troubles here than hot engines.

The _only_ thing you should be doing now is opening the radiator and adding coolant if it needs any -- do this when the engine is cold. Beyond that, stop obsessing. When the needle makes regular forays to the 3/4 mark, then you have something to complain about. Wait for the needle to move 1/3 to 1/2 of the distance from Normal to Hot, then start looking for ways to spend your money.

I swear to God, it you ever complain of the needle moving 1mm again, I'm coming over to your house to slap you. You are complaining about a perfectly normal condition.

If _anything_, you have experienced the first pangs of pain from a thermostat that sticks closed, although that is very rare in a BMW. A t-stat that is stuck closed is a huge problem, and the most common failure mode for BMW is that they stick open. I'm not sure how this happens, but cold engines are far and away more common reports of t-stat troubles here than hot engines.

The _only_ thing you should be doing now is opening the radiator and adding coolant if it needs any -- do this when the engine is cold. Beyond that, stop obsessing. When the needle makes regular forays to the 3/4 mark, then you have something to complain about. Wait for the needle to move 1/3 to 1/2 of the distance from Normal to Hot, then start looking for ways to spend your money.

The T-Stat in my 3 series went bad and got stuck closed a couple times...

Uy yuy yuy! I did the easter egg gauge reset as I found on the UK web site stated above. The guages all go through some sort of diagnostic thing and cycle through their full sweep. The coolant guage is back to normal. No more 1 mm high side offset. So - If your guage goes north by about a millimeter and you're reasonably confident your cooling system is tickety-boo, do the odo reset exercise for test #21. Chances are it will fix this issue. I'll post back if it returns but for now it's back to normal.

I even noticed the low guage reading is back to just on, or even to the left of the lower white hash mark on the guage. Must be my guages don't like being left outside when the temperature is below 10°F.

I'm in complete agreement with others that posted here regarding bigger excursions of the guage. If it make large and sudden excursions, doesn't stray far from blue (cold), or moves around a lot, it's telling you there are cooling system issues that need to be addressed. This 1 mm guage thing is just that - a guage gremlin. It's NOT your cooling system.

Most all auto manufacturers buffer their temp guages so they stay put under normal operation. Dealers don't want customers pestering them with imaginary cooling problems.

One thing to keep in mind is that the guage isn't exactly timely when reporting cooling issues. When the expansion tank popped in my 325i last year I saw a large cloud of steam coming from my grille and shut the engine down before the guage even budged from 12 o'clock. The low coolant light came on first. The best advice I can give is: know your cooling system and try to adhere to the old school maintenance schedule.

Last edited by Bim3Por911; 01-23-2012 at 11:08 PM.
Reason: I spell like an enjuneer.

Drove to work this morning and the guage position is normal just like before the 1 mm movement incident. Resetting the gauges using the #21 test sequence on the odo pixel display seems to have sent the guage gremlin away.

The gauge problem came back on my car, until I replaced my eight year old battery and the weather warmed up. I re-did the #21 trick and now it's been gone now for a couple of weeks. It makes me think it's related to the health of the electrical system.

I realize this post is fairly old but, as I am experiencing the same "needle to the right" issue and have been doing large amounts of trouble-shooting to determine the cause... I figured I'd post.

First thing: There are lots of arguments that say because the gauge is "buffered" there is no need to pay attention to a gauge that was previously at a solid 12-oclock position just because it has shifted slightly.This is faulty logic- if the gauge is buffered to read the exact same position while the coolant is within a range of temperatures (for example, 90-96C) then the only reason the needle would start to move at all within that temperature range would have to be because the buffering is failing.

Otherwise, 90-96C (normal op temp) would be buffered and return dead-center 12-oclock as normal, no? a buffered gauge would be just that, buffered, and any normal temp would result in a dead-center, 12-oclock reading. That would be the very definition of buffered: many possible readings resulting in ONE output-> dead-center, 12-oclock.

So, if the engine coolant is actually within normal operating range, and the -buffered- guage is now showing slightly higher than -normal for that gauge- then either the gauge is/has become faulty or the buffering control-loop is failing in some fashion.

Second: I am going through this on my 2001 325Ci and have been for about a year. My engine temp rarely reads dead-center 12-oclock, which it used to for the first 10 years of the car's life, it now reads 1-4mm to right of dead-center 12-oclock. It varies depending on my driving, and sudden acceleration and slow-downs.

Also, once the needle shifts slightly to the right, it remains slightly to the right even when I shut the car off: it won't read a normal 0-cold it reads the same 1-4mm higher than cold.

This 1-4mm shift has 99% of the time been accompanied by: P0128 code.

Over the course of the last 1yr + troublshooting I've replaced: 2 new radiators and an electric radiator fan, water pump, 2 aux cooling fans (first was defective and locked up after 4 months), both temp sensors (radiator hose and engine block), battery is only 2 years old and is fine, alternator is now brand new and let's not forget the original 3 coolant thermostat's I went through before believing there was more to this issue.

The thermostats!

First thermostat /with new water-pump and radiator w/ elec fan (took some road damage) installed at same time: Car was fine for 4-5 months- then the car almost over-heated, figured for sure defective thermostat P0128 was the issue, luckily got to a garage before it touched the red-line, although it was only a couple mm's away on the guage. Second thermostat installed.

Second thermostat: ran hot, it would fluctuate between center and the white line at the high-end of the normal operating range. It would look like it was ready to exceed the normal portion of the guage but never quite make it into the top third of gauge near red. Still definitely not normal. Installed third-thermostat.

Third thermostat: 1-4mm above dead-center, depending on driving. No other outputs. During the life of third-thermostat so far: the second new radiator, new alternator, both new temp sensors and both new mechanical aux cooling fans. Only since the new second radiator in the last week has the code P0128 not shown up again... yet.

Losing my mind trying to figure this out.
Tech at local BMW place said in some instances the DME on car's my age need reprogramming for a newer updated version of the thermostat they are shipping these days? I haven't confirmed or delved into that yet.

As I've mentioned, for the first 10years of this car's life, dead-center 12-oclock no matter what. Instrument cluster (gauge) has NOT changed.
Just about everything else has.

My next steps are to: try to confirm that story about the DME possibly needing a quick update to read the newer thermostats correctly (as unlikely as I think that is), and possibly replace my new water pump again. Maybe it was defective and has been providing low-flow since 5 months after it's installation.

I hope someone has fun reading this and even more I hope someone at some point has figured out what this possible electrical gremlin could be.

I'm starting to suspect some dying capacitor on the DME board not properly outputting a signal to the instrument cluster... shot in the dark?

Any input would be appreciated.

Thanks guys.

Been reading for 5 years, never had an issue I couldn't solve with previous pots and never seen an issue that I could help more than others who'd already commented.

So the real question is what is your coolant temperature actually running and what is your outside temp?

The DME reflash may not really be a solution for you??

Are we dealing with a warm running engine, a coolant gauge issue or both?

Assuming the thermostat heater never works, the engine cooling temp should stat steady near 93-95C at temps below 70F from what I have seen, not sure how much more the temps will creep above this in warmer climates.

Is there any likelihood that an original plastic impeller water pump may have lost a piece that may be wedged the motor? Not sure these water pumps have this problem, but other engines with plastic water pumps have has this type of problem.